Chemistry Reference
In-Depth Information
factors that play important roles in microbial attachment (often irreversible) and
biofilm formation [19, 26].
Although biofilms play a crucial role in bio-geochemical cycling and can be
beneficial in some biotechnological processes (e.g., wastewater treatment) they
can also be a menace for purification and separation processes, water distribution
systems, ship hulls, cooling towers, clinical and biomedical devices, and
processes in the pulp and paper industry [28-33]. In addition to causing odor and
taste problems, biofilms are resistant to conventional disinfectants and difficult to
remove because of their mechanical stability owing to EPS[34]. Most
microorganisms are capable of forming biofilms under the appropriate
environmental and developmental conditions and the EPS are responsible for
providing favorable milieu for the deposition of microorganisms and biofilm
propagation. It has been proposed that development of antifouling strategies
should be based on analysis of fouling factors and the biofilm properties[31].
Despite decades of research devoted towards understanding biofilm formation
mechanisms[18, 19, 26, 35-41] there is still a considerable knowledge gap in
specific molecular level role of EPS components in governing the biofilm
formation necessitating more research in this subject [20, 23, 42-44]. For instance,
there is a wide consensus that the microbial floc formation is known to depend on
total EPS concentration as well as its specific components [27, 45-48].
Therefore, our research has focused on developing detailed information on
molecular components of EPS secreted during microbial growth and biofouling
processes, which in turn would provide insights on the specific EPS components
that promote biofouling and biofilm formation. Recently, we have reported that
sub-minimum inhibitory concentrations (sub-MIC) of bismuth thiols could be
utilized as the probing agents for understanding specific molecular-level role of
cell-bound and free-EPS in bacterial flocculation and adhesion under un-inhibited
growth conditions[15, 49, 50]. Other investigations have also shown that bismuth
thiols could inhibit biofilm formation on stents, catheters, and water distribution
systems[51-53]. We believe that this approach of increasing bismuth solubility by
chelating it with appropriate ligands will advance the knowledge of biofilm
growth and properties and inspire the development of bismuth-based
antimicrobial and antibiofouling strategies.
The objective of this chapter is to summarize the use of two-forms of bismuth
thiols: (1) the cationic-form for studying the molecular-level role of EPS in
governing bioflocculation processes during planktonic growth of bacteria, and (2)
the zero-valentnanoparticle-form for creating novel antibacterial and antifouling
surfaces. Three formulations of bismuth thiols, namely, bismuth
dimercaptopropanol (BisBAL), bismuth ethanedithiol (BisEDT), and bismuth
